The present invention relates to antennae, and, in particular, to devices for actively changing the antenna structure.
In the past, microwave antennae have been constructed having a fixed frequency response therein. This fixed response can not be changed to accommodate different operating frequencies. However, many systems, such as aircraft, require antennae operating over multiple frequency bands. Thus, there exists a need for a means of changing an antenna's structure upon command to control the operating frequency of the antenna.
At equilibrium, a semiconductor is semi-insulating, and therefore appears as a dielectric. Illuminating a region of a semiconductor substrate with light of a preselected wavelength results in the generation of free carriers in the substrate and allows the creation of a conductive region (semi-metallic) in the substrate. The generated conductive region can function as an antenna operating over a specific frequency range and with a set radiation pattern. Thus by controlling the pattern of light projected onto the semiconductor substrate, the frequency and radiation pattern of the antennae can be changed.